Ballistic vest

ABSTRACT

The invention relates to a ballistic vest containing a stack of flexible fabrics and a stack of flexible unidirectional layers, in which the fabrics contain strong fibres of a first kind, the unidirectional layers contain strong fibres of a second kind, and in which the fibres in a unidirectional layer run essentially parallel and are disposed at an angle to fibres in an adjacent layer which is greater than 0 degrees, where in that the flexible fabric is a loose fabric and is located on the strike side of the vest.  
     The percentages by weight of the loose fabrics and the stack of UD layers preferably is between 15:85 and 30:70%. In that case, a vest of areal density IGSS than 6 kg/m 2  can have such ballistic resistance as to stop an Action a bullet with a velocity of up to 437 m/s with a trauma to NIJ Standard of less than 44 mm.

[0001] The invention relates to a ballistic vest containing a stack offlexible fabrics and a slack or flexible unidirectional layers, in whichthe fabrics contain strong fibres of a first kind, the unidirectionallayers contain strong fibres of a second kind, and In which the fibresIn a unidirectional layer run essentially parallel and are disposed atan angle to fibres in an adjacent layer which is greater than 0 degrees.The invention more particularly relates to vests that provide protectionagainst hollow-point bullets.

[0002] Changing threats in the form of new types of bullet requireprotective garment designs to be adapted time and again. It hasappeared, for example. that none of current vest designs offersprotection against a new type of bullets (Action 3 bullets), whichbecause of their hollow point tend to remain lodged in the body.Protection against this type of bullet requires a vest weight so high asto cause discomfort.

[0003] Vests that protect against different threats are known in the artU.S. Pat. No. 5,926,842, for example, discloses a ballistic vestconsisting of a stack of flexible plain weave fabric layers and a stackof flexible unidirectional layers, herein referred to as UD layers, inwhich the fibres run essentially parallel and are disposed of at anangle of 90 degrees to the tibres in an adjacent layer. Such a stack ofat least two cross-plied UD layers is herein referred to as a UDcross-ply. U.S. Pat. No. 5,026,842 teaches that the UD cross-plies arepreferably located on a strike side 25 of the vest. A vest of this kindwith an areal density of approx. 4.9 kg/m² offers, for example,protection against threats such as those specified in the NIJ2 and NIJ2astandards.

[0004] In seeking protection against Action 3 bullets, various designsfrom U.S. Pat. No. 5,926,842 were tested. These tests indicated thatfabric, whether or not in combination with high tensile strengthpolyethylene fibres in a UD cross-ply assembly for a vest according tothe assemblies in U.S. Pat. No. 5,926,842, only offers protectionagainst Action 3 bullets with a velocity of 430 m/s if the areal densityof the vest is at least 6.5 kg/m². Such high areal density substantiallyreduces the vest's wearing comfort.

[0005] The object of the invention is to provide a vest with a lowerareal density that offers protection against Action 3 bullets.

[0006] This object is achieved according to the invention by theflexible fabric being a loose fabric and being located on the strikeside of the vest. This ensures that a vest of the invention with arealdensity of less than 6 kg/m² offers protection against Action 3 bullets.

[0007] A loose fabric here and hereinafter means a fabric the yams inwhich can readily move relative lo one another. Such a fabric is alsodeformable Surprisingly, it has been found that a vest provided with aloose fabric on the strike side of the vest offers improved protectionagainst Action 3 bullets. Also, the vest at the invention, with lowerareal density, can offer tne same protection as a vest that does notcontain a loose fabric on the strike side.

[0008] An advantage of the vest of the invention is that it is morecomfortable to wear because of its lower weight.

[0009] The ballistic resistance of a vest can be classified according tovarious standards. One such standard is NIJ Standard 0101.03, whichdefines various levels of protection A vest to the NlJ2a standard muststop for example a .357 Magnum JSP with a velocity of 381 m/s and also a0 mm FMJ with a velocity of 332 m/s.

[0010] A vest to the NIJ3a standard must stop a .44 Magnum SWC at 426m/s and a 9 mm FMJ at 426 m/s. In addition to preventing projectilepenetration, the extent to which the body side deforms behind an impactis a second requirement of NIJ Standard 0101.03. This deformationmeasures the trauma cxperienced by the wearer of a vest on impact of aprojectile. An advantage of the vest of the invention is that, despiteits lower weight, deformation on the body side of the vest meets therequirement of NIJ Standard 0101.03.

[0011] Loose fabrics may be for example twill weave, honeycomb weave,cord weave or three-dimensional fabrics. It is essential here that thefabric be a drapable one. A drapable fabric generally is a fabric inwhich the number of floats is at least 3, which means that the fabriccontains yams that at the same time cross at least 3 other yarns.

[0012] Preferably, the fibres in the loose fabrics are alsosubstantially stretched. Non-wovens were found not to contribute tostopping Action 3 bullets.

[0013] It is preferred for the loose fabric to be a twill weave fabric.I will weave fabrics are fabrics in which the warp and weft do not crossone another at a 1:1 ratio, as they do in a fabric with plain weave, butat a ratio other than 1:1. In for example a 4.1 twill weave fabric, theweft crosses 4 warp yarns on one side of the fabric, 1 warp yarn on theother side of the fabric and so forth. The number of floats in such afabric is 1. It is preferred for the fabric of the invention to be a 5.1twill weave. This provided the highest protection against Action 3bullets at the lowest vest weight.

[0014] The stack of UD layers may consist of one UD package or aplurality of UD packages. The stack of UD layers preferably consists ofa plurality of UD packages each of which contains two or four UD layers.Preferably, the packages are provided with a smooth film on both sides,resulting in reduced friction between the packages and higherflexibility of the stack.

[0015] “Fibers” should here be understood to mean elongated bodies whoselength is substantially larger than the width and thickness. Fibrescomprise continuous monofilaments and multifilaments as well asdiscontinuous filaments such as staple fibres or cut fibres.

[0016] In general, the percentages by weight of the stack of loosefabrics and the stack of UD layers in the vest may be between 10.80 and50.50%. If the percentage by weight of loose fibres is less than 10%, adisproportionately high number of UD layers need to be added to thevest, causing the advantage of lower weight to be lost. If thepercentage by weight of loose fibres is greater than 50 % any additionallayers of twill fabric contribute less than proportionately toprotection against Action 3 bullets, again causing the advantage oflower weight to be lost.

[0017] It is preferred for the percentages by weight of the stack ofloose fabrics and the stack of UD layers to be between 15:85 and 30:70&.

[0018] This ensures that a vest of the invention with a first and secondstack, which together have an areal density of less than 6 kg/m², hassuch ballistic resistance as to stop an Action 3 bullet with a velocityof up to 437 m/s with a trauma to NIJ Standard of less than 44 mm.

[0019] This also ensures that a vest of the invention, in which thefirst and second stack have a total areal density of less than 5.2kg/m², has a ballistic resistance such that the vest complies with theNIJ3a standard.

[0020] This also ensures that a vest of the invention with a first andsecond stack, which together have an areal density of less than 4.5kg/m², has such ballistic resistance as to stop an Action 3 bullet witha velocity of up to 385 m/s with a trauma to NIJ Standard of less than44 mm.

[0021] “Strong fibres” of a first or second kind may be of differentkinds or of the same kind and in the present invention generally arefibres with a strength of at least 6 dN/tex, a modulus of at least 130dN/tex and a fracture energy of at least 6 J/g. Strong fibres preferablyare fibres with a strength of at least 10 dN/tex, a modulus of at least200 dN/tex and a fracture energy of at least 20 J/g. Strong fibres morepreferably are fibres with a strength of at least 16 dN/tex. a modulusof at least 400 dN/tex and a fracture energy of at least 27 J/g. Strongfibres most preferably are fibres with a strength of at least 28 dN/tex,a modulus of at least 1200 dN/tex and a fracture energy of at least 40J/g. If the fibres of the first kind do not have the same strength asthe fibres of the second kind, it is recommended that the fibres of thefirst kind be stronger than the fibres of the second kind.

[0022] Suitable strong fibres are fibres of aramid, polybenzazole (PBO),silicium carbide and/or a reinforced polymer such as drawn ultra-highmolecular weight polyethylene (HPPF) ;and/or combinations thereofUltra-high molecular weight polyetiylene means polyethylene with aweight-average molecular weight of at least 500,000 kg/kmol.

[0023] It is preferred for the molecular weight to be greater than2,000,000 kg/kmol. It is preferred for the vest of the invention to havea stack of UD layers in which the UD layers mainly contain aramid or PBOfibres. This ensures that a vest in which the first and second stackhave a combined areal density of less than 4 kg/m² has such ballisticresistance as to stop an Action 3 bullet with a velocity of up to 385m/s with a trauma to NIJ standard of less than 44 mm.

[0024] An advantage of the vest of the invention is that a constructionin which unidirectional layers are replaced with loose fabrics offersimproved protection against certain types of ammunition including Action3 bullets. Given that loose fabrics are much simpler to produce, theproduction costs of a vest of the invention are lower than those ofknown vests consisting solely of UD layers.

[0025] Ballistic fabrics such as those applied in known vests arepredominantly tightly woven fixed fabrics, often with a yarn having aslow a titre as possible. Both the manufacture of yarns and themanufacture of fabrics therefrom is much more costly than themanufacture of UD cross-ply.

[0026] The titre of the yarns for the loose fabric need not meet anyparticular requirements. It is preferred, however, for the vest at theinvention to contain a fabric package in which the fabric essentiallyconsists of yarns with a titre of at least 1000 dTex. With such yarnsbetter results are achieved than with fabric packages from yarns with atitre of less than 1000 dTex. An additional advantage of yarns with ahigher titre is that both the yarns and the fabric formed therefrom canbe produced more cheaply than yarns with a lower titre.

[0027] The invention is elucidated with reference to some examples.

[0028] Areal density (AD) of a fabric or UD layer or package means theweight of a fabric or UD layer per unit area.

[0029] UD-SB2 is a package of four cross plied layers in which thefibres in each layer run substantially in parallel and are disposedperpendicularly to the fibres in an adjacent layer, with each layerbeing fabricated of HPPE yarns (Dyneema®). The yarn weight per layer is26 g/m². The UD-SB2 package contains a rubber matrix and is covered onboth sides with a PE film. An UD-SB2 package has an AD of 155 g/m².

[0030] UD-SB21 is a package of four cross-plied layers in which thefibres in each layer run substantially in parallel and are disposedperpendicularly to the fibres in an adjacent layer, with each layerbeing fabricated of HPPE yarns (Dyneema®). The yarn weight per layer is26 g/m². The UD-SB21 package contains a rubber matrix and is covered onboth sides with a PE film. An UD-SB21 package has an AD of 145 g/m².

[0031] Goldflex is a 4-layer cross-ply UD based on 1000 dTex aramidyarns with an AD of 233 g/m².

[0032] W557 is a 5.1 twill weave fabric with the warp and the weftconsisting of a 1700 dTex HPPE yarn (Dyneema®). The areal density of afabric layer is 270 g/m². The fabric is loose and well drapable.

[0033] Aramid fabric is a non-deformable plain weave fabric based on 930dTex aramid yarn (Twaron® TC) with an AD of 200 g/m².

[0034] Twaron VD0461 is a fixed, non deformable fabric based on 3360dTex aramid yarn with an areal density of 475 g/m²

[0035] Fraglight® is a nonwoven based on HPPE staple fibre of more than880 dTex with an AD of 205 g/m².

[0036] In all examples and comparative experiments. the fabric waspositioned on the strike side of a fabric-cum-UD vest unless expresslyotherwise stated.

Example I

[0037] Vests of a stack of 20 packages of UD-SB2 and 5 layers of W557with total areal density of 5.85 kg/M² were fired at with Action 3 (A3)bullets at 440, 432, 433, 430 and 437 m/s.

[0038] None of the bullets fully penetrated. This observation is highlysurprising given that the fabric concerned was a fairly coarse fabricmade of {fraction (1/60)} dTex Dyneema® yarn. The development in the artof ever better ballistic fabrics until now went in the direction of theuse of increasingly finer fabrics with, in addition, an increasinglylower areal density per layer. This direction is opposite of the one ofthe present invention using loose fabrics.

Example II

[0039] A vest of a stack of 20 packages of UD-SB2 and 4 layers of W557was fired at with A3 bullets at 385 m/s. The vest, with AD of 4.2 kg/m²,showed no full penetration. In comparison with the vest referred to inExample 1, which stops A3 bullets at 430 m/s, this vest is lighter for385 m/s than might be expected in light of the energy absorption in thevest with AD of 5.85 kg/m² .

Example III

[0040] A vest of a stack of 12 packages of aramid cross-ply-UD(Goldflex) and 4 layers of W557 was fired at with A3 bullets at 385 m/s.The vest, with AD of 3.9 kg/m², showed no full penetration.

Example IV

[0041] A vest of a stack of 20 packages of US-SB2 and 4 layers of a 3 1twill weave fabric at {fraction (1/60)} d Tex yarns AD per layer of 275g/m², AD at the vest is 4.4 k/m²) was filed at 362, 378, 416, 422, 430and 431 m/s.

[0042] Full penetration was found to have occurred at 378 and 430 m/sStops were found at 362, 422 and even at 431 m/s. Because of theinconsistency (full penetration) at 378 and a slop a 431 m/s) a 2 ^(nd)vest of the same composition was tested, result: 1 full penetration at431 m/s, for the rest only stops. that is. at 407, 415, 426, 431, 433,425 and 436 m/s. Thus, this fabric in combination with SB2 makes itpossible to stop A3 bullets but seems less consistent because of fullpenetration at 378 m/s.

Example V

[0043] Firing tests were conducted in accordance with the NIJ2 standard,with a vest of a stack of 20 packages of UD-SB2 and 4 layer of W557being tested with the 9 mm at 360 m/s and the .357 Magnum at 425 m/s. Nofull penetration was observed in either case. Thus, a vest of a stack of20 packages of UD-SB2 and d layers of W557 with AD of 4.2 kg/m² meetsthe NIJ standard.,The current recommendation for an SB-2 vest that meetsthe NIJ 2 standard is a stack of 20 packages of UD-SB2 with AD of 4.5kg/m².

Example VI

[0044] Firing tests were conducted in accordance with the NIJ3a standard

[0045] a. with 9mm: A vest of a stack of 20 packages of UD-SB2 and 4layers of W557 was fired at with 9mm at 425 m/s. Next, V50 wasdetermined.

[0046] Three stops were found at 425 m/s and the V50 was 401 m/s.

[0047] b. with .44 Magnum: A vest of a stack of 26 packages of UD-SB2and 4 layers of W557 was fired at with .44 Magnum at 425 m/s and nextV50 was determined. Three stops were found at 425 m/s with a traumasmaller than 44 m and V50 was 476 m/s.

[0048] Conclusion: A vest of a stack of 26 packages of UD-SB2 and 4layers of W557 with AD of 5.1 kg/m² complies with the NIJ3a standard for9 mm and .44 Magnum. The current SB2 recommendation for meeting thisstandard is a vest of a stack of UD-SB2 packages of 5.3 kg/m² .

Example VII

[0049] Testing of protection against Ranger SXT+P+ammunition. Similarlyto Action 3 bullets, this is a Jacketed Hollow Point bullet.

[0050] A vest of a stack of 20 packages of UD-SB2 and 4 layers of W557(AD of 4.2 kg/m2) was tested with Ranger SXT 9 mm bullets at 425 m/s.

[0051] Stops were found at 421 and 425 m/s with traumas of 33 and 35 mm,respectively.

[0052] Since the vest tested here was identical to the vest in Example Vand the vest in Example VI contained 6 extra UD-SB2 packages, this meansthat the vests for NIJ2 and NlJ3a in Examples V and VI also stop RangerSXT+P+bullets. Example IIX

[0053] A vest of a stack of 20 packages of UD-SB2 and 4 layers of aloose, readily deformable plain weave fabric (368 g/m²), in which boththe warp and weft incorporated 5 parallel HPPE 1760 dTex yarns (5floats), was filed at with A3 bullets at 410 m/s. No full penetrationwas found to have occurred in the vest, with AD of 4.6 kg/m².

Example IX

[0054] A vest of a stack of 20 packages of UD-SB2 and 3 layers of aloose, readily deformable cord weave fabric (287 g/m2) with 3 and morefloats. made of 1760 dTex HPPE was fired at with A3 bullets at 410 m/s.The vest, with AD of 1.3 kg/m², did not reveal full penetration.

Example X

[0055] Vests of a stack of 20 packages of UD-SB21 and 4 layers of W557with total areal density of 4 kg/m2 were fired at with FSP fragments inorder to determine V50.

[0056] V50 was found to be 549 m/s.

Example XI

[0057] Vests of a stack of 20 packages of UD-SB21 and 4 layers of W557with total areal density of 4 kg/m2 were fired at with 9 mm copperjacket bullets. Stops were found at 383 m/s. The trauma depth was 25-35mm.

Example XII

[0058] Vests at a stack of 18 packages of UD-SB21 and 4 layers of W557with total areal density of 3.7 kg/m2 were fired at with TSP fragmentsin order to determine V50.

[0059] V50 was found to be 523 m/s. This shows that the vest of theinvention has an unexpectedly high V50 against TSP fragments at this lowareal density. Consequently, the energy absorption per unit of arealdensity is extraordinarily high.

Example XIII

[0060] Vests of a stack of 18 packages of UD-SB21 and 4 layers of W557with total areal density of 3.7 kg/m² were fired at with standard 9 mmbullets. Stops were found at 382 m/s. The trauma depth was 29-38 mm.

Example XIV

[0061] Vests of a stack of 18 packages -of UD-SB21 and 4 layers of W557with total areal density of 3.7 kg/m² were fired at with 9 mm cu jacketbullets. Stops were found at 382 m/s The trauma depth was 24-33 mm.

Example XV

[0062] Vests of a stack of 18 packages of UD-SB21 and 4 layers of W557with total areal density of 3.7 kg/m2 were fired at with 9 mm SXT rangerbullets. Stops were found at 375 m/s. The trauma depth was 26-31 mm.

Comparative Experiment A

[0063] Firing tests were conducted with A3 bullets and packages ofdifferent compositions.

[0064] The results were as follows:

[0065] a) A vest of 12 layers of aramid fabric and a stack of 29packages of UD-SB2 with AD of 6.9 kg/m² exhibited penetration at 411m/s.

[0066] b) A vest of 20 layers of aramid fabric and a stack of 14packages of SB2 with AD of 6.2 kg/m² exhibited penetration at 442 m/s.

[0067] c) A vest of 21 layers of aramid fabric and a stack of 9 packagesof UD S82 with AU of 6.2 kg/m² exhibited penetration at 436 m/s.

[0068] d) A vest of 28 layers of aramid fabric and a stack of 4 layersof SB2 with AD of 6.2 kg/m² exhibited penetration at 436 m/s.

[0069] e) A vest of 31 layers of aramid fabric with AD of 6.2 kg/m²exhibited penetrations at about 430 m/s.

[0070] f) A vest of 18 layers of aramid fabric behind a stack of 20packages of UD-SB2 with AD of 6.9 kg/m² exhibited a full penetration at417 m/s.

[0071] g) A vest of 10 layers of fraglight in front of a stack of 20packages of UD-SB2 with AD of 6.5 kg/m² exhibited a full penetration atabout 421 m/s.

[0072] h) It took a vest of 21 packages of W557 with AD of 5.7 kg/m² tostop A3 at 385 m/s.

[0073] i) A vest of 51 packages of UD-SB2 with AD of 7.9 kg/m² provedinadequate to stop A3 bullets with a velocity of 400 m/s.

[0074] j) The number of layers of aramid fabric needed to stop an A3bullet with a velocity of 430 m/s was determined. It appeared that thistakes a stack of 31 layers with AD of 6.5 kg/m².

Comparative Experiment B

[0075] Starting from 20 packages of UD SB2, it was determined how manylayers of a non-deformable plain weave aramid (Twaron VD 0461) fabric ofyarns with a titre Of 3360 dTex, positioned in front of the stack ofUD-SB2 packages, are needed to stop A3 bullets. It was found that 20packages of UD-SB2 and 8 layers of aramid fabric with AD of 6.8 kg/M²are needed to stop A3. This is substantially more than the 4.2 kg/m²found for the combination of UD-SB2 and W557.

Comparative Experiment C

[0076] Vests of approx. 3.2 kg/m² were prepared in order to measure astandard ballistic performance of the various materials. Next, V50 wasdetermined for 9 mm parebellum. Material Layers AD (kg/m²) V50 (m/s) SB220 3.1 439 W557 12 3.2 <295 Twaron CT 16 3.2 353 930 dTex Twaron 7 3.3<304 VD0461

[0077] These results confirm the impression that a loose fabric alonegives a lower level of performance: the Dyneema W557 and Twaron VD0401fabrics cannot even stop the 9 mm bullet at approx. 300 m/s. The resultsalso indicate that SB2 scores better than an aramid fabric based onTwaron CT 930 dTex with a comparable areal density.

1. Ballistic vest containing a stack of flexible fabrics and a stack offlexible unidirectional layers, in which the fabrics contain strongfibres of a first kind, the unidirectional layers contain strong fibresof a second kind, and in which the fibres in a unidirectional layer runessentially parallel and are disposed at an angle to fibres in anadjacent layer which is greater than 0 degrees characterised In that theflexible fabric Is a loose fabric and Is located on a strike side of thevest.
 2. Vest according to claim 1, in which the loose fabric containsat least 3 floats.
 3. Vest according to claim 1 or claim 2, in which theloose fabric is a twill weave.
 4. Vest according to any one of claims1-3, in which the percentages by weight of the stack of loose fabricsand the stack of UD layers is between 15:85 and 30:70%.
 5. Vestaccording to any one of claims 1-4, in which the first and second stacktogether have an areal density of less than 6 kg/m² and in which thevest has such ballistic resistance as to stop an Action 3 bullet with avelocity of up to 437 m/s with a trauma to NIJ Standard of less than 44mm.
 6. Vest according to any one of claims 1-4. In which the first andsecond stack together have an areal density of less than 4.5 kg/m² andin which the vest has such ballistic resistance as to stop an Action 3bullet with a velocity of up to 385 m/s with a trauma to NIJ Standard ofless than 44 mm.
 7. Vest according to any one of claims 1-4, in whichthe first and second stack together have an areal density of less than5.2 kg/m² and in which the vest has such ballistic resistance as tocomply with NIJ3a Standard 0101.03.
 8. Vest according to any one ofclaims 1-7, in which the unidirectional layer contains mainly aramid orpolybenzazole (PBO) fibres.
 9. Vest according to any one of claims 8, inwhich the first and second stack together have an areal density of lessthan 4 kg/1m² and in which the vest has such ballistic resistance as tostop an Action 3 bullet with a velocity of up to 385 m/s with a traumato NIJ Standard of less than 44 mm.
 10. Vest according to any one ofclaims 1-9 in which the fabric is a 5.1 twill weave fabric.